1. Field of the Invention
The present invention relates to generally to a method and apparatus for data transmission and reception, and more particularly, to a method and apparatus for data transmission and reception utilizing Multiple-Input and Multiple-Output (MIMO) precoding based on Distributed Antenna Systems.
2. Description of the Related Art
In a Distributed Antenna System (DAS), the Central Processing Unit (CPU) for processing signals is connected through wired/wireless networks with transmit antennas evenly distributed within an entire cell so that a User Equipment (UE) may form a virtual cell together with multiple nearby transmit antennas. Due to a distribution of transmit antennas over a wide area, a DAS may provide an advantage of macroscopic diversity, as well as provide high-speed and high-quality communication services to UEs located on cell boundaries. The DAS may increase system capacity by decreasing inter-cell interference through a reduction of transmit power of individual transmit antennas. Hence, distributed antenna systems are expected to be a core technology in next-generation wireless communication systems.
In the event that the CPU is connected with M (spatially distributed) Distributed Antenna Ports (DAP), where M is the number of ports, and each DAP is associated with nT transmit antennas, downlink data generated by the CPU may be transmitted simultaneously through MnT transmit antennas. A receiver may receive signals using multiple receive antennas. Accordingly, a DAS may contribute to effective downlink transmission through Multiple-Input/Multiple-Output (MIMO) technology.
DAS channel environments are significantly different from channel environments of existing co-located MIMO channels. In particular, as propagation paths between a UE and DAPs in one cell are very different, a significant difference is present between average channel gains with respect to the different DAPs. In addition, channels between transmit antennas of the same DAP and a UE are correlated, while channels between transmit antennas of different DAPs and a UE are uncorrelated. Accordingly, both correlated and uncorrelated channel conditions may coexist in DAS channel environments. As existing MIMO precoding schemes may be inadequate for DAS channel environments, there is a need for a new MIMO precoding scheme suitable to DAS channel environments. In order to achieve effective DAS-based downlink data transmission, a new MIMO precoding scheme adequate for DAS channel properties is needed.